On Wed, 16 May 2012, Sarah Sharp wrote:
> There are several different exit latencies associated with coming out of
> the U1 or U2 lower power link state.
>
> Device Exit Latency (DEL) is the maximum time it takes for the USB
> device to bring its upstream link into U0. That can be found in the
> SuperSpeed Extended Capabilities BOS descriptor for the device. The
> time it takes for a particular link in the tree to exit to U0 is the
> maximum of either the parent hub's U1/U2 DEL, or the child's U1/U2 DEL.
...
> --- a/include/linux/usb.h
> +++ b/include/linux/usb.h
> @@ -378,6 +378,39 @@ enum usb_device_removable {
> USB_DEVICE_FIXED,
> };
>
> +/*
> + * USB 3.0 Link Power Management (LPM) parameters.
> + *
> + * PEL and SEL are USB 3.0 Link PM latencies for device-initiated LPM exit.
> + * MEL is the USB 3.0 Link PM latency for host-initiated LPM exit.
> + * All three are stored in nanoseconds.
> + */
> +struct usb3_lpm_parameters {
> + /*
> + * Maximum exit latency (MEL) for the host to send a packet to the
> + * device (either a Ping for isoc endpoints, or a data packet for
> + * interrupt endpoints), the hubs to decode the packet, and for all hubs
> + * in the path to transition the links to U0.
> + */
> + unsigned long long mel;
Do these have to be long long? Are any of the values ever going to be
bigger than 1 second?
> @@ -507,6 +540,8 @@ struct usb_device {
> struct wusb_dev *wusb_dev;
> int slot_id;
> enum usb_device_removable removable;
> + struct usb3_lpm_parameters u1_params;
> + struct usb3_lpm_parameters u2_params;
No kerneldoc entries added for these two new fields.
Alan Stern
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